Develop an iOS version of an existing android app

General information for the business: We provide advanced technology solutions
Kind of development: Customization of existing program
Description of requirements/functionality: To develop an iOS version of an existing android app. This App will showcase some of the museums highlights, contact information and events calendar. Currently the android app targets API 22. The app must be designed to accommodate screen sizes from iPhone4 to iPhone 7 Plus & iPad, iPad pro and iPad mini 4. The platforms we are interested are preferably the ‘Xcode’ and ‘AppCode’. We are open to suggestions for any other platforms such as ‘Code runner’.
Currently the android work flow is managed using BitBucket and Sourcetree. We would prefer if the work flow for the iOS is done under the same platform. Communication will predominantly be via ‘Trello’ and ‘Slack’. ‘Trello’ will classify the tasks to be completed with the deadlines and ‘slack’ for any immediate communication whilst the App is being built. Any other communication can be carried out via skype and email. Regular milestones will be set by us and will be followed by a review. All app information will be shared via a secure drop box.
We would also require the freelancer to propose a robust pre-release iOS app testing plan.
Extra notes: